RÉSUMÉ
A bioassay-guided fractionation of leaf extracts from Clytostoma callistegioides (Cham.) Bureau ex Griseb. (Bignoniaceae) led to isolation of a natural mixture of four fatty acids with anti-insect activity against aphids. The compounds were identified by GC-MS as palmitic, stearic, linoleic and linolenic acids and quantified as their methyl esters. The anti-aphid activity of the natural mixture was traced to linolenic and linoleic acids, as shown by the settling inhibition activity of synthetic samples. Interestingly, the saturated acids (palmitic and stearic) tested alone stimulated settling on one of the tested aphids (Myzus persicae), but not on the other tested species (Rhopalosiphum padi). Although ubiquitous, none of these free acids have been previously reported in this Bignoniaceae species. The leaf surface chemistry, which is likely involved in modulating aphid settling behavior, was further investigated for the occurrence of lipophilic substances by histochemical staining. Short, stalked glandular trichomes, previously undescribed for this species, stained with osmium tetroxide and Sudan III, suggesting that the secretion of the defensive acids is related to these surface trichomes.
Sujet(s)
Aphides/effets des médicaments et des substances chimiques , Bignoniaceae/composition chimique , Acides gras/isolement et purification , Acides gras/pharmacologie , Comportement alimentaire/effets des médicaments et des substances chimiques , Animaux , Acides gras/composition chimique , Chromatographie gazeuse-spectrométrie de masse , Acides linoléiques/composition chimique , Acides linoléiques/isolement et purification , Acides linoléiques/pharmacologie , Acides linoléniques/composition chimique , Acides linoléniques/isolement et purification , Acides linoléniques/pharmacologie , Acides palmitiques/composition chimique , Acides palmitiques/isolement et purification , Acides palmitiques/pharmacologie , Feuilles de plante/composition chimique , Acides stéariques/composition chimique , Acides stéariques/isolement et purification , Acides stéariques/pharmacologie , Cires/composition chimique , Cires/métabolismeRÉSUMÉ
A new cytotoxic compound, brasilibactin A (1), has been isolated from the actinomycete Nocardia brasiliensis IFM 0995, and the structure was elucidated on the basis of spectroscopic data and chemical means.
Sujet(s)
Antinéoplasiques/isolement et purification , Nocardia/composition chimique , Acides stéariques/isolement et purification , Animaux , Antinéoplasiques/composition chimique , Antinéoplasiques/pharmacologie , Tests de criblage d'agents antitumoraux , Humains , Cellules KB , Leucémie L1210 , Souris , Acides stéariques/composition chimique , Acides stéariques/pharmacologieRÉSUMÉ
O fracionamento cromatográfico do extrato hexânico das partes aéreas de Cambessedesia espora DC - Melastomataceae levou ao isolamento dos ácidos palmítico, mirístico e esteárico, ß-Silosterol e do triterpeno fern-9(11)-en-3ß-ol. As substâncias foram identificadas por métodos espectroscópicos usuais (RMN, IV, CG/EM).
Sujet(s)
Extraits de plantes/composition chimique , Plantes/composition chimique , Acide myristique/isolement et purification , Acides stéariques/isolement et purification , Acides gras/isolement et purification , Acides palmitiques/isolement et purification , Chromatographie sur couche mince , Spectrophotométrie , Spectrophotométrie IR , Triterpènes/isolement et purificationRÉSUMÉ
The human immunodeficiency virus (HIV) epidemic has altered the epidemiological profile of tuberculosis in both industrialized and developing countries. Serious diseases caused by mycobacteria other that M. tuberculosis, mostly belonging to the M. avium-intracellulare complex (MAC), have become very common in association with severe immunosuppression. The increase in mycobacterial disease complexity has stimulated the development of more rapid and efficient methods of diagnosis. In the present study we characterized the cellular fatty acids and the mycolic acid cleavage product from most frequent mycobacteria species in Argentina using gas chromatography in order to develop a rapid technique for their identification. Fatty acids and mycolic acids extracted from saponified mycobacterial cells were examined as methyl esters by capillary has chromatography. The major constituent fatty acids in all species, with the exception of M. smegmatis, were octadecenoic (18:1) and hexadecanoic (16:1) acids. The fatty acids and mycolic acid cleavage product profiles from the studied species were quantitatively but not qualitatively different. Tuberculostearic acid was found in all species. Significantly different amounts of some fatty acids (p < 0.01) were observed among clinical isolates of M. tuberculosis, M. bovis and MAC. Traces of 2-eicosanol were detected in the M. tuberculosis H37Rv strain. Although a limited number of strains and species were tested, preliminary results indicate that this method could be used to characterize mycobacterial cultures.